1. Field of the Invention
The present invention relates generally to semiconductor memories and, more particularly, to methods of programming semiconductor memories.
2. Description of Related Art
Charge-trapping memories, which have been referred to as flash memories, find extensive use in a wide range of electronic devices including cameras, cellular telephones and personal digital assistants as well as modems, laptop computers and the like. Charge-trapping memories are capable of storing relatively large amounts of data in a small space. Data stored in charge-trapping memories maintains its integrity even in the absence of applied power.
A cell of a charge-trapping memory can be programmed by modifying a threshold voltage associated with the cell. Reading data from the cell can be accomplished by applying a reference voltage and detecting a current level. A cell that is programmable to one of two distinguishable threshold levels for storage of one bit of information is commonly called a single-level cell (SLC). When, for example, four or eight distinguishable threshold levels can be supported by the cell, the cell can be capable of storing, respectively, two or four bits of data. A cell that can store more than one bit of data has been referred to as a multi-level cell (MLC).
The time required to program a charge-trapping memory can be relatively large compared to that required simply to read from or write to the memory. In applications involving electronic devices where data is to be stored as rapidly as possible (e.g., in a digital camera), lengthy programming times can act to hamper efficiency of operation of the memory to the detriment of overall device performance.
A need thus exists in the prior art to reduce the programming time in charge-trapping memories.